The present invention relates to valves for admitting granular solid materials flowing under the force of gravity into spaces enclosing gas under greater pressure than that in the spaces from which the solid materials are flowing through the valve assembly.
In order to use the heat energy potentially available in some materials which have previously been wasted, it is possible to burn such materials in furnaces depending primarily on the combustion of more conventional fuels, by adding smaller quantities of waste material, usually in comminuted form, to the primary conventional fuel. Thus, it is desirable to add secondary fuels such as comminuted rubber tire waste to the flow of primary fuel and air flowing through a pneumatic fuel feed line into a furnace firebox. Such a mixture, because of the steel wire content of tire waste material, is useful in balancing the chemistry in lime kilns in production of cement. Because of the chemistry involved, it is necessary to add such secondary fuels to the flow of the primary fuel in such a process in controlled amounts.
The primary fuel used in firing a lime kiln, may, for example, be powdered coal carried in a stream of air through a pressurized pneumatic fuel delivery line. When adding secondary fuel to such a line it is necessary to prevent escape of the pressurized flow of fuel and air, since the powdered coal would constitute a hazard to health and present a risk of a dangerous fire. To be most effective a valve assembly for use in such a situation must permit the secondary fuel to flow freely through the valve assembly into the stream of pressurized gas and fuel mixture without escape of the pressurized fuel and air mixture in the direction opposite the flow of the secondary fuel into the pressurized pneumatic fuel delivery line.
A previously available device for the purpose generally of admitting granular or lumpy materials from a low pressure zone into a higher pressure zone has been quite expensive, because of its massive construction and its use of pneumatic cylinder-and-piston assemblies controlled by a timer to operate an upper, non-airtight batch gate, and a pair of lower, airtight sealing gates in a desired sequence.
What is needed, therefore, is an improved and less expensive valve assembly for use in introducing lumpy or granular materials into zones of higher pressure without reverse flow of material through the valve assembly from the higher pressure zone.